media: staging/intel-ipu3: Fix race condition during set_fmt

Do not modify imgu_pipe->nodes[inode].vdev_fmt.fmt.pix_mp, until the
format has been correctly validated.

Otherwise, even if we use a backup variable, there is a period of time
where imgu_pipe->nodes[inode].vdev_fmt.fmt.pix_mp might have an invalid
value that can be used by other functions.

Cc: [email protected]
Fixes: ad91849 ("media: staging/intel-ipu3: Fix set_fmt error handling")
Reviewed-by: Tomasz Figa <[email protected]>
Signed-off-by: Ricardo Ribalda <[email protected]>
Signed-off-by: Sakari Ailus <[email protected]>
Signed-off-by: Mauro Carvalho Chehab <[email protected]>

drivers/staging/media/ipu3/ipu3-v4l2.c

@@ -669,7 +669,6 @@ static int imgu_fmt(struct imgu_device *imgu, unsigned int pipe, int node,
 	struct imgu_css_pipe *css_pipe = &imgu->css.pipes[pipe];
 	struct imgu_media_pipe *imgu_pipe = &imgu->imgu_pipe[pipe];
 	struct imgu_v4l2_subdev *imgu_sd = &imgu_pipe->imgu_sd;
-	struct v4l2_pix_format_mplane fmt_backup;
 
 	dev_dbg(dev, "set fmt node [%u][%u](try = %u)", pipe, node, try);
 
@@ -687,6 +686,7 @@ static int imgu_fmt(struct imgu_device *imgu, unsigned int pipe, int node,
 
 	dev_dbg(dev, "IPU3 pipe %u pipe_id = %u", pipe, css_pipe->pipe_id);
 
+	css_q = imgu_node_to_queue(node);
 	for (i = 0; i < IPU3_CSS_QUEUES; i++) {
 		unsigned int inode = imgu_map_node(imgu, i);
 
@@ -701,6 +701,11 @@ static int imgu_fmt(struct imgu_device *imgu, unsigned int pipe, int node,
 			continue;
 		}
 
+		if (i == css_q) {
+			fmts[i] = &f->fmt.pix_mp;
+			continue;
+		}
+
 		if (try) {
 			fmts[i] = kmemdup(&imgu_pipe->nodes[inode].vdev_fmt.fmt.pix_mp,
 					  sizeof(struct v4l2_pix_format_mplane),
@@ -729,39 +734,32 @@ static int imgu_fmt(struct imgu_device *imgu, unsigned int pipe, int node,
 		rects[IPU3_CSS_RECT_GDC]->height = pad_fmt.height;
 	}
 
-	/*
-	 * imgu doesn't set the node to the value given by user
-	 * before we return success from this function, so set it here.
-	 */
-	css_q = imgu_node_to_queue(node);
 	if (!fmts[css_q]) {
 		ret = -EINVAL;
 		goto out;
 	}
-	fmt_backup = *fmts[css_q];
-	*fmts[css_q] = f->fmt.pix_mp;
 
 	if (try)
 		ret = imgu_css_fmt_try(&imgu->css, fmts, rects, pipe);
 	else
 		ret = imgu_css_fmt_set(&imgu->css, fmts, rects, pipe);
 
-	if (try || ret < 0)
-		*fmts[css_q] = fmt_backup;
-
 	/* ret is the binary number in the firmware blob */
 	if (ret < 0)
 		goto out;
 
-	if (try)
-		f->fmt.pix_mp = *fmts[css_q];
-	else
-		f->fmt = imgu_pipe->nodes[node].vdev_fmt.fmt;
+	/*
+	 * imgu doesn't set the node to the value given by user
+	 * before we return success from this function, so set it here.
+	 */
+	if (!try)
+		imgu_pipe->nodes[node].vdev_fmt.fmt.pix_mp = f->fmt.pix_mp;
 
 out:
 	if (try) {
 		for (i = 0; i < IPU3_CSS_QUEUES; i++)
-			kfree(fmts[i]);
+			if (i != css_q)
+				kfree(fmts[i]);
 	}
 
 	return ret;